5872-22-0Relevant academic research and scientific papers
Phosphine-Catalyzed Doubly Stereoconvergent γ-Additions of Racemic Heterocycles to Racemic Allenoates: The Catalytic Enantioselective Synthesis of Protected α,α-Disubstituted α-Amino Acid Derivatives
Kalek, Marcin,Fu, Gregory C.
supporting information, p. 9438 - 9442 (2015/08/11)
Methods have recently been developed for the phosphine-catalyzed asymmetric γ-addition of nucleophiles to readily available allenoates and alkynoates to generate useful α,β-unsaturated carbonyl compounds that bear a stereogenic center in either the γ or t
Bispalladacycle-catalyzed Michael addition of in situ formed azlactones to enones
Weber, Manuel,Jautze, Sascha,Frey, Wolfgang,Peters, René
supporting information, p. 14792 - 14804 (2013/01/15)
The development and further evolution of the first catalytic asymmetric conjugate additions of azlactones as activated amino acid derivatives to enones is described. Whereas the first-generation approach started from isolated azlactones, in the second-generation approach the azlactones could be generated in situ starting from racemic N-benzoylated amino acids. The third evolution stage could make use of racemic unprotected α-amino acids to directly form highly enantioenriched and diastereomerically pure masked quaternary amino acid products bearing an additional tertiary stereocenter. The step-economic transformations were accomplished by cooperative activation by using a robust planar chiral bis-Pd catalyst, a Br?nsted acid (HOAc or BzOH; Ac=acetyl, Bz=benzoyl), and a Br?nsted base (NaOAc). In particular the second- and third-generation approaches provide a rapid and divergent access to biologically interesting unnatural quaternary amino acid derivatives from inexpensive bulk chemicals. In that way highly enantioenriched acyclic α-amino acids, α-alkyl proline, and α-alkyl pyroglutamic acid derivatives could be prepared in diastereomerically pure form. In addition, a unique way is presented to prepare diastereomerically pure bicyclic dipeptides in just two steps from unprotected tertiary α-amino acids. Flourishing step economy: The evolution of the catalytic asymmetric addition of azlactones to enones is described. The first-generation approach started from isolated azlactones. In the second-generation approach azlactones could be generated in situ from racemic N-benzoylated amino acids. The third evolution stage could directly use racemic unprotected α-amino acids to form a large number of highly enantioenriched quaternary amino acids derivatives (see figure). Copyright
1-Azadienes in Heterocyclic Synthesis. Reaction of 1-N-Alkyl-1-azapenta-1,3-dienes with Mesoionic Oxazolones
Sain, B.,Sandhu, J. S.
, p. 1007 - 1010 (2007/10/02)
1-N-Alkyl-1-azapenta-1,3-dienes 2 smoothly reacted with various mesoionic oxazolones 1 to afford 3,4-dihydro-2-pyridones 3 in excellent yields and there is no evidence for the formation of any products arising from the cycloaddition on the carbon-carbon double bond or on the azomethine function.
